Fluid mechanics Flashcards
dynamic fluid forces
drag
lift
concerned with the movement of liquids and gases
drag force
slows something down
the resistance force caused by the motion of a body travelling through a fluid
acts in the opposite direction to motion so has a negative effect on velocity
produced from air resistance and friction
surface drag
relates to friction between the surface of an object and the fluid environment
swimmers wear specialised smooth clothing and shave body hair to reduce surface drag
can be called skin drag
form drag
relates to the impact of the fluid environment on an object.
the forces affecting the leading edge of an object increase form drag and the forces affecting the trailing edge reduce form drag.
swimmers create the thinnest and straightest form as they move to decrease form drag
cyclists use slipstreams to reduce form drag
can be called shape drag
factors that reduce and increase drag:
the velocity of the moving body
the greater the velocity of a moving body through a fluid, the greater the drag force
streamlining the body reduces drag
factors that reduce and increase drag:
the cross-sectional area of the moving body
a large cross sectional area increases drag
crouching low over handlebars reduces drag
speed skiers crouching low to reduce drag and travel faster
factors that reduce and increase drag:
the shape and surface characteristics of a moving body
a more streamlined, aerodynamic shape reduces drag
speed skiers have helmets that extend to their shoulders
the Bernoulli principle
where air molecules exert less pressure the faster they travel and more pressure when they travel slower
25-40*
discus experiences and upwards lift force meaning it stays in the air for longer so travels further.
the angle of attack changes the flow of air around the discus.
the air that travels below the discuss has less distance to cover so travels at a slower velocity creating a higher pressure.
this creates upward lift force
